1. Field of the Invention
The present invention relates to tools for disassembling universal joints, and more specifically to two different types of tools--a pull-type tool and a push-type tool --for disassembling universal joints of vehicles.
2. Description of Prior Art
There are various situations in which it is necessary to disassemble the universal joint of the drive shaft of a vehicle. For example, prior to towing vehicle with the drive wheels remaining on the ground, it is necessary to disconnect the transmission from the drive axles to protect the vehicle from damage during towing. This is generally achieved by disconnecting the drive shaft universal joint at the drive axle pinion yoke, or occasionally by pulling the drive axle shafts. However, substantial problems are often encountered when disassembling the universal joint.
Specifically, although new universal joint components are shiny and have accurately machined fits, and can be assembled easily, even when in dry condition, once a vehicle has been used for a year or more without disassembling the drive shaft universal joint, the universal joint soon becomes rusted due to wet roads and/or salty roads, so that the universal joint components become so tightly assembled that it is virtually impossible to disassemble them.
Faced with such a problem, mechanics and towing/wrecker crews often resort to hammering the universal joint components apart, but that is very destructive to the components. In addition, even that technique is often not effective or is difficult to carry out, especially when it has to be done at night on cold, wet roads with merely a flashlight as a light source. The problems are further compounded by the fact that, in towing situations, there is usually very little room in which to work.
In response to the above-discussed problems, a mechanical puller apparatus for disassembling universal joints has been developed, and is disclosed in U.S. Pat. No. 4,019,233 to Jirele. The apparatus or tool disclosed in that patent employs a driver screw which is rotated mechanically or manually to exert a downward force on a bridge assembly connected to a first yoke member of the universal joint, while an upward pulling force is exerted on bosses connected to the second yoke member of the universal joint by means of puller arms which are threadably connected to the driver screw.
Small hand pullers of the type described in the aforementioned patent have significant drawbacks. Notably, since such pullers are operated by manual force, their effectiveness varies from user to user, and often they are ineffective to do the job. In addition, such small hand pullers are not effective for the purposes of towing and wrecker crews, in that working conditions on the road (poor lighting, inclement weather, insufficient working space, and so forth) render manual pullers even less effective.
A further disadvantage of the manual puller described in the aforementioned patent resides in the fact that, in the use of such a "rotating screw" tool, many unwanted reaction forces are produced when the screw is rotated manually, and this interferes with the successful accomplishment of the universal joint disassembly operation. This problem, together with the aforementioned problems of poor working conditions, results in the consumption of excessive time as the user attempts to disassemble the universal joint. Finally, it will be recognized that puller-type tools such as disclosed in the aforementioned patent are bulky, and this is a disadvantage not only from the standpoint of using the tool, but also from the standpoint of transporting the tool to the worksite.
Large, industrial-type tools are available in the marketplace, and are used for pulling assembled components apart, or pushing components out of an assembly. Such large, industrial-type tools often employ electric motors or pneumatic-powered hydraulic power packs, and occasionally hand-powered units are employed in conjunction with closed hydraulic circuits. The following U.S. patents disclose such types of hydraulic-powered apparatus or arrangements: U.S. Pat. No. 2,807,081 to Black; U.S. Pat. No. 3,069,761 to Sommer; and U.S. Pat. No. 3,908,258 to Barty.
However, such powered apparatus or arrangements are burdened by several disadvantages. They are usually very large and bulky, and are therefore not suitable for transport to and from towing or wrecker worksites, and are also not suitable for use under the adverse conditions often encountered by towing and wrecker crews. In addition, such industrial-type powered apparatus often operate under hydraulic power, and accordingly require auxiliary hydraulic sources to power their operation, thus increasing their bulkiness and non-portablity. Finally, such apparatus or arrangements as disclosed in the latter three patents are simply not suitable or adaptable for use in the specific application of disassembling universal joints.
Other disassembly or pushing/pulling tools or apparatus, even less applicable to the job of disassembling drive shaft universal joints, are disclosed in the following U.S. patents: U.S. Pat. No. 2,950,525 to Duncan et al; U.S. Pat. No. 3,337,943 to Powell; U.S. Pat. No. 3,339,263 to Dodge; U.S. Pat. No. 1,498,933 to Seppmann; U.S. Pat. No. 2,507,003 to Gagne; U.S. Pat. No. 2,566,847 to Miller; U.S. Pat. No. 3,230,617 to Spiess et al; U.S. Pat. No. 3,927,462 to Freeman et al; and U.S. Pat. No. 4,182,011 to Bretzger et al.
To summarize, the state of the prior art in this area of technology is such that it would be considered highly desirable and advantageous to have a tool or apparatus which is specifically designed for the disassembly of drive shaft universal joints, especially under adverse road conditions as usually encountered by towing and wrecker crews. Such drive shaft universal joint disassembly tools should have the following characteristics: they should be portable and easily transportable to the worksite; they should be powered so as to facilitate their use, especially under conditions of limited space and adverse working conditions; and they should be powered by some power source normally available to towing and wrecker crews at the worksite.